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Sake is fine, but keep it in moderation.
Literal
Sake [also-も] good [but-が] moderate [to-に] do-[preparatory-ておく][gentle-command-なさい].
A gentle parental admonition. 大概にする is a fixed phrase meaning 'to keep in moderation, to not overdo it.' 大概 originally meaning 'mostly, generally' has specialized here into 'within reasonable limits.' ~ておく adds a 'have (the action) done in advance, ready' nuance — here reinforcing 'keep it at that level.' ~なさい is the gentle parental imperative. も ('also, even') in 酒も acknowledges sake as one acceptable thing among others.